21/12 - American Heart Association Updates Recommendations for Blood Pressure Measurements

Dec. 20, 2004 — The American Heart Association has updated its 1993 recommendations for blood pressure measurements. The new guidelines that are published in the February issue of Hypertension emphasize out-of-office blood pressure readings, proper cuff size, and more.

"Since the last statement, there have been huge changes in the technology used to measure blood pressure and in our knowledge about the significance of different measurements," lead author Thomas G. Pickering, MD, DPhil, from Columbia University Medical Center in New York, NY, says in a news release. "We've found that blood pressure measurements taken by doctors in their offices may actually be unreliable in many patients. For that reason, there is wider acceptance of blood pressure readings taken by patients in their homes, and of 24-hour ambulatory blood pressure monitoring."

Patients should monitor their blood pressure at home, using validated devices, and they should inform their physicians of these readings to facilitate management. In the event of a discrepancy between out-of-office and in-office measurement, physicians should consider the out-of-office readings provided that the readings were reliably recorded. Evidence suggests that home readings predict cardiovascular events and are especially useful to monitor the effects of treatment.

Compared with office measurements, ambulatory monitoring for 24 hours is a better predictor of cardiovascular risk and can help diagnose white-coat hypertension. The guidelines also note that ambulatory blood pressure can help identify people with hypertension who do not experience the usual nocturnal drop in blood pressure, which is important because these individuals may be at higher cardiovascular risk.

"The 1993 document didn't say much about home and ambulatory monitoring, but now there is much more emphasis on out-of-office measurements and less exclusive reliance on traditional methods of measurement," Dr. Pickering says.

Although this new focus on out-of-office readings is the most significant change, the guidelines also recommend using the proper cuff size, as the use of too large or too small cuffs is the most common error in blood pressure measurement.

When blood pressure is measured in the medical setting, the guidelines recommend that the cuff be placed on bare skin after the patient has relaxed for several minutes, and the patient should be seated comfortably in a chair with the back and arm supported, legs uncrossed, and not talking.

In the office or hospital, the mercury sphygmomanometer, using the first and fifth phases of the Korotkoff sounds, is still the preferred method for blood pressure measurement. However, these devices are gradually being replaced, in part because of environmental concerns about mercury contamination.

Aneroid devices are a suitable alternative, but they require frequent calibration. Hybrid devices using electronic transducers instead of mercury may prove to be a valid option. Although the oscillometric method can be used to take multiple measurements in the office, only devices independently validated by standard protocols should be used, and individual calibration is preferred.

"Alternative devices can become inaccurate, so calibration with a mercury reading is critical to ensuring accuracy," Dr. Pickering notes.

Even when automated devices are used, those responsible for recording blood pressure must be properly trained to reduce human sources of error. According to the guideline committee, regulatory agencies should establish standards to ensure the use of validated devices, routine calibration of equipment, and the training and retraining of manual observers.

"Accurate measurement of blood pressure is essential to classify individuals, to ascertain blood pressure-related risk, and to guide management," the panel concludes. "The objective of this report is to provide clinicians with a standardized set of recommendations that, if followed, should lead to accurate estimation of blood pressure."

Hypertension. 2005;45:2-21